This invention relates to tires generally and more specifically to tires having a composite ply structure including at least one primary ply of inextensible radial extending cords, most preferably of fine diameter steel cords primarily for use in passenger pneumatic or light truck tires, including, not limited to, runflat type tires.
The use of radial steel cords in tires is well known in the tire art, earthmover and commercial truck tires have used steel corded tires for years.
As the use of steel cords is attempted in passenger tires some common problems of how to consistently make a ply turnup of a steel cord reinforced ply must be resolved.
Historically one must first ask the question of whether or not a ply turnup is even needed.
In 1921 Charles Miller in U.S. Pat. No. 1,393,952 taught that plies could be securely anchored to the beads by means of fabric strips having crossed strands relative to the ply cords without any of the plies actually wrapping around the bead core. Miller""s tires showed that as few as four plies were possible, a breakthrough for the tires of that era.
In 1942, S. M. Elliott in U.S. Pat. No. 2,430,560 reported that farm tires could be made with greater elastic deformation if the bead wrapping fabric strips did not even contact the body plies. A radical departure from what was otherwise accepted practice.
In 1968, Fred Kovac and Grover Rye of Goodyear patented a bias tire leaving an outer ply having giant cords of 0.037 inches or greater. This outer ply comprised two parts, a bias body ply and a pair of radial bead plies. The edges of the bead plies overlapped the edges of the body plies and are sandwiched between them. Kovac et al indicated that the body ply may be of wire and the bead plies may be reinforced with fabric or filament. Kovac pointedly notes that if giant cords are used in the carcass, the plies containing them are so stiff that it is difficult for the tire builder to turn them around the beads. Thus, he recommended that the edges of the stiffer plies stop short of turning under the beads and bead plies of softer fabric are turned under the beads with their edges overlapping the edges of the stiffer plies.
Powers et al. of The Firestone Tire and Rubber Company taught a radial play pneumatic tire having one or more body plies containing radially directed inextensible cords with the ply ends terminating on the same side of the bead bundle as the ply. The tire further having a bead connector ply containing radial, inextensible reinforcing cords which is wrapped about the bead bundle. Powers et al noted that a prior art British Patent No. 990,524 disclosed a radial ply body and a radial ply bead wrap, the cords of the body ply being rayon cords and the bead wrap being steel cord reinforced. Powers noted that the differences in modulus resulted in the cords not acting together as if they were one ply, whereas his all-inextensible cord design did act as one ply. Powers taught that the body ply and the bead connecting ply, where they are contiguous to one another, must be at least 20% and not greater than 50% of the peripheral distance of the body ply as measured from the midpoint of the bead bundle along the body ply to the point on the body ply where the edges of the tread ply are located. Powers suggest glass, steel or Keviar cords could be used. The Powers et al test tire was a 11-22.5 truck tire employing 1xc3x974+6xc3x974xc3x970.175+1xc3x970.15 radial cords of steel wire of a cable construction having 14 ends per inch. Similarly, the bead connector used the same steel wire construction. These truck tires carry a high operating inflation pressure of about 100 psi and the Powers et al patent demonstrated a potentially feasible concept although no known commercialization of such a truck tire had occurred.
In 1995, Ahmad et al disclosed a pneumatic tire having a discontinuous outer carcass ply. Ahmad et al disclosed a full radially inner ply with a conventional turnup end and a discontinuous outer carcass ply that extended from under the belt edges to the bead the outer ply being contiguously in contact with the outer ply.
EPO Publication 822195A2 disclose a Runflat Tire and Method which shows a runflat tire having multiple radial plies wherein at least one ply is wrapped about the bead and has a turnup, the remaining plies simply terminate near the bead. The bead area concept appears similar to the prior art solutions disclosed in Ahmad with the exception that the plies are spaced by fillers or inserts a common feature of runflat tires.
The present invention provides a novel way of creating a composite ply structure in a tire. The tire can be a radial ply pneumatic tire including the type known as runflat tires.